1. Field of Invention
This invention pertains to a method and device of transmitting digital information at a high data rate over several relatively low data rate communication channels.
2. Description of the Prior Art
It is known that the rate of data communication over leased data channels is limited by the maximum speed of said channels and the modems used to interface with the channels. In order to overcome this barrier an LSD (Line Sharing Device) has been used. This device, also known as an N-plexer, receives data bits at a high rate from a DTE (Data Transmitting Equipment) and distributes these data bits to several modems which operate at a lower bit rate than the bit rate of the DTE. Each modem encodes its share of the bits into corresponding analog signals, which then are transmitted over leased data channels. At the receiving end several modems, one per channel, are used to demodulate the signals and a second LSD is used to re-assemble the low speed demodulated signals into a single high speed bit stream.
However this scheme requires the use of several complete modems in addition to the LSD. Furthermore complications arise if several different types of data channels are used simultaneously because they could introduce delays in the system.